1. Field of the Invention
The present invention relates to a chemical liquid valve arranged such that a valve element coupled to a driving device is brought into/out of contact with a valve seat placed between an inlet port and an outlet port.
2. Description of Related Art
In a conventional manufacturing line for semiconductors, medical products, and others, a chemical liquid valve has been used to control a chemical liquid such as purified water, acid, and alkali. FIG. 11 is a sectional view of a chemical liquid valve 100 in a prior art.
The chemical liquid valve 100 has a body 103 formed with an inlet port 101 and an outlet port 102, and a diaphragm 105 held between the body 103 and a bonnet nut 104. The diaphragm 105 is fixed with a valve element 106 placed across the center of the diaphragm 105. The diaphragm 105 is arranged to bring the valve element 106 into/out of contact with a valve seat 107 formed between the inlet port 101 and the outlet port 102. Threadably mounted in the bonnet nut 104 is a slide shaft 108 whose top is secured with a handle 109. The slide shaft 108 is formed, in its bottom, with a recess 110 in which the upper portion of the valve element 106 is placed. A ring washer 111 is fit on the upper portion of the valve element 106, which is supported by the ring washer 111 engaged in a large-diameter portion 112 of the recess 110. Accordingly, when the handle 109 is turned to move the slide shaft 108 up/down, moving the valve element 106 up/down, a valve opening degree can be controlled. A bearing 113 is further provided between the valve element 106 and the slide shaft 108 to prevent the valve element 106 from turning together with the slide shaft 108 (see Japanese unexamined patent application publication No. 11-182708(1999) for example).